I think my betta has fin rot?

Question
I think my betta has fin rot but I can't tell. His fins used to be a real pretty blue. I first started to notice when he wasn't moving very much he soend most of his time at the bottom of his tank just sitting there he moves every once in a while most of the time when I turn the light on and off he'll get up and explore a little bit but then he has back to the bottom he has stopped eating he acknowledges the food but doesn't eat. I noticed that back edge of his caudel fin looks like its been injured or something it's looks brown almost in the spot the the edes of his fins are starting to look the same I think and its almost like you can see through them in the light. Does this sound like fin rot? I bought the fin rot medicine from petco but im afraid to use it what if he doesn't have fin rot and it kills him ? I don't what to do I have had him for little under a year and im very attached to him :(  

Answer
Hello Andie-

Yup, that sounds like fin rot to me. Thankfully, it's usually not fatal in bettas unless they develop a secondary infection, and it sounds like you are well prepared to start treatment.

Go ahead and start the medication (if it is Melafix, by chance, be sure not to overdose and change 50%-70% of the water weekly.) With other medications, just follow the instructions and be sure to keep the water fresh and clear. You can also try a small bit of aquarium salt (or Melafix, if you're not using it as a main treatment) to help kill the infection and promote regrowth of the fins.

Hope this is useful! Feel free to write back with any other questions.
-Amber Worman